Elderly Parents and Looking Out for Them

My Mom is 74 and she's determined that she's not old but a lot of shit is getting hard to ignore. She still goes horseback riding fairly regularly and wants to be out on the 4 wheelers fixing fence and chasing cattle and whatnot. She can still do it pretty well but it surprises me how weak and incapable she is a lot of the time. She can't get gates open or closed that I can do without even exerting any force. She couldn't get the cap off of our portable fuel tank the other day and when I took it off for her I couldn't even pretend that it was tight. She's in good shape and health for her age but the physical decline is just undeniable. One of our neighbors is 75 and has been a horse guy all his life but just got a new horse a few weeks ago and it bucked him off and broke his pelvis. He could already barely walk because of past horse injuries but he's determined to get back in the saddle. I think he'd be way better off to accept reality and stop while he can still function at all, but on the other hand, people who quit living their lives tend to die pretty quickly so who knows?